Percentile Health Dictionary

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Percentile: From 1 Different Sources

The set of numbers from 0 to 100 that divide a distribution into 100 parts of equal area, or divide a set of ranked data into 100 class intervals, with each interval containing 1/100 of the observations. For example, the 5th percentile, is a cut point with 5% of the observations below it and the remaining 95% of the observations above it.
Health Source: Community Health
Author: Health Dictionary

Weight And Height

Charts relating height to age have been devised, and give an indication of the normal rate of growth. (See APPENDIX 6: MEASUREMENTS IN MEDICINE for more details.) The wide variation in normal children is immediately apparent on studying such charts. Deviations from the mean of this wide range are called percentiles. Centile or percentile charts describe the distribution of a characteristic in a population. They are obtained by measuring a speci?c characteristic in a large population of at least 1,000 of each sex at each age. For each age there will be a height, above and below which 50 per cent of the population lies: this is called the 50th centile. The 50th centile thus indicates the mean height at a particular age. Such tables are less reliable around the age of PUBERTY, because of variation in age of onset.

Minor variations from the mean do not warrant investigation, but if the height of an individual falls below the third centile (3 per cent of normal children have a height that falls below the third centile) or above the 97th centile, investigation is required. Changes in the rate of growth are also important, and skeletal proportions may provide useful information. There are many children who are normal but who are small in relation to their parents; the problem is merely growth delay. These children take longer to reach maturity and there is also a proportional delay in their skeletal maturation – so that the actual height must always be assessed in relation to maturity. The change in skeletal proportions is one manifestation of maturity, but other features include the maturing of facial features with the growth of nose and jaw, and dental development. Maturity of bone can readily be measured by the radiological bone age.

Failure to gain weight is of more signi?cance. Whilst this may be due to some underlying disease, the most common cause is a diet containing inadequate calories (see CALORIE). Over the last six decades or so there has been quite a striking increase in the heights and weights of European children, with manufacturers of children’s clothing, shoes and furniture having to increase the size of their products. Growth is now completed at 20–21 years, compared with 25 at the turn of the century. It has been suggested that this increase, and earlier maturation, have been due to a combination of genetic mixing as a result of population movements, with the whole range of improvement in environmental hygiene – and not merely to better nutrition.

In the case of adults, views have changed in recent years concerning ‘ideal’ weight. Life-insurance statistics have shown that maximal life expectancy is obtained if the average weight at 25–30 years is maintained throughout the rest of life. These insurance statistics also suggest that it is of advantage to be slightly over the average weight before the age of 30 years; to be of average weight after the age of 40; and to be underweight from ages 30–40. In the past it has been usual, in assessing the signi?cance of an adult’s weight, to allow a 10 per cent range on either side of normal for variations in body-build. A closer correlation has been found between thoracic and abdominal measurements and weight.... weight and height


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